From patchwork Thu Apr 14 13:07:30 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 561735 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A8B8BC43217 for ; Thu, 14 Apr 2022 13:45:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245055AbiDNNrA (ORCPT ); Thu, 14 Apr 2022 09:47:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36424 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245592AbiDNNio (ORCPT ); Thu, 14 Apr 2022 09:38:44 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B5509A5EA2; Thu, 14 Apr 2022 06:33:07 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 52ADC6122A; Thu, 14 Apr 2022 13:33:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 68588C385A1; Thu, 14 Apr 2022 13:33:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649943186; bh=44lVM/amND90feArpe5TIR64rOXZwEf0h4oD2/g9f/Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ldZTS/hvh1ZpkdYfwcDB2mSm0i9K16jJcX/mJsHXyegtrUDBArpSaJIEFEL0Sovxl jzG8oJaT39Dz9AQJGFTZy4y/8gVljGlshBiy+BF4iS3OaWN4w7TDLWImKi1Nz5VM68 aKN/8F+cIUsFPB1bw1GRcaai91OVNwVZm/fcAwnU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tejun Heo , Josef Bacik , Jens Axboe Subject: [PATCH 5.4 065/475] block: dont merge across cgroup boundaries if blkcg is enabled Date: Thu, 14 Apr 2022 15:07:30 +0200 Message-Id: <20220414110856.972671765@linuxfoundation.org> X-Mailer: git-send-email 2.35.2 In-Reply-To: <20220414110855.141582785@linuxfoundation.org> References: <20220414110855.141582785@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Tejun Heo commit 6b2b04590b51aa4cf395fcd185ce439cab5961dc upstream. blk-iocost and iolatency are cgroup aware rq-qos policies but they didn't disable merges across different cgroups. This obviously can lead to accounting and control errors but more importantly to priority inversions - e.g. an IO which belongs to a higher priority cgroup or IO class may end up getting throttled incorrectly because it gets merged to an IO issued from a low priority cgroup. Fix it by adding blk_cgroup_mergeable() which is called from merge paths and rejects cross-cgroup and cross-issue_as_root merges. Signed-off-by: Tejun Heo Fixes: d70675121546 ("block: introduce blk-iolatency io controller") Cc: stable@vger.kernel.org # v4.19+ Cc: Josef Bacik Link: https://lore.kernel.org/r/Yi/eE/6zFNyWJ+qd@slm.duckdns.org Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/blk-merge.c | 11 +++++++++++ include/linux/blk-cgroup.h | 17 +++++++++++++++++ 2 files changed, 28 insertions(+) --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -7,6 +7,7 @@ #include #include #include +#include #include @@ -571,6 +572,9 @@ static inline unsigned int blk_rq_get_ma static inline int ll_new_hw_segment(struct request *req, struct bio *bio, unsigned int nr_phys_segs) { + if (!blk_cgroup_mergeable(req, bio)) + goto no_merge; + if (blk_integrity_merge_bio(req->q, req, bio) == false) goto no_merge; @@ -662,6 +666,9 @@ static int ll_merge_requests_fn(struct r if (total_phys_segments > blk_rq_get_max_segments(req)) return 0; + if (!blk_cgroup_mergeable(req, next->bio)) + return 0; + if (blk_integrity_merge_rq(q, req, next) == false) return 0; @@ -885,6 +892,10 @@ bool blk_rq_merge_ok(struct request *rq, if (rq->rq_disk != bio->bi_disk) return false; + /* don't merge across cgroup boundaries */ + if (!blk_cgroup_mergeable(rq, bio)) + return false; + /* only merge integrity protected bio into ditto rq */ if (blk_integrity_merge_bio(rq->q, rq, bio) == false) return false; --- a/include/linux/blk-cgroup.h +++ b/include/linux/blk-cgroup.h @@ -22,6 +22,7 @@ #include #include #include +#include /* percpu_counter batch for blkg_[rw]stats, per-cpu drift doesn't matter */ #define BLKG_STAT_CPU_BATCH (INT_MAX / 2) @@ -768,6 +769,21 @@ static inline void blkcg_use_delay(struc atomic_inc(&blkg->blkcg->css.cgroup->congestion_count); } +/** + * blk_cgroup_mergeable - Determine whether to allow or disallow merges + * @rq: request to merge into + * @bio: bio to merge + * + * @bio and @rq should belong to the same cgroup and their issue_as_root should + * match. The latter is necessary as we don't want to throttle e.g. a metadata + * update because it happens to be next to a regular IO. + */ +static inline bool blk_cgroup_mergeable(struct request *rq, struct bio *bio) +{ + return rq->bio->bi_blkg == bio->bi_blkg && + bio_issue_as_root_blkg(rq->bio) == bio_issue_as_root_blkg(bio); +} + static inline int blkcg_unuse_delay(struct blkcg_gq *blkg) { int old = atomic_read(&blkg->use_delay); @@ -868,6 +884,7 @@ static inline bool blkcg_punt_bio_submit static inline void blkcg_bio_issue_init(struct bio *bio) { } static inline bool blkcg_bio_issue_check(struct request_queue *q, struct bio *bio) { return true; } +static inline bool blk_cgroup_mergeable(struct request *rq, struct bio *bio) { return true; } #define blk_queue_for_each_rl(rl, q) \ for ((rl) = &(q)->root_rl; (rl); (rl) = NULL)